γ-戊内酯/亚临界水梯度提取秦岭箭竹半纤维素机理及其分子结构研究

Bamboo is one of the most important resources in forestry of China, the content of hemicelluloses is second to that of cellulose, besides, they have wide application prospect in chemical processing of bamboo industry. However, up to now, it has lacked the research on the mechanism for clean and efficient extraction of hemicelluloses, which results in molecular degradation and environmental pollution during the extraction processes of hemicelluloses with alkali and organic solvents. Therefore, the high-value conversion of bamboo hemicelluloses was seriously restricted. In this project, it would be based on the study of bonding mechanism for hemicelluloses in bamboo Fargesia qinLingensis. Subsequently, the hemicelluloses fractions with more homogeneous structure will be obtained by gradient extraction with the clean system of γ-valerolactone/subcritical water from bamboo Fargesia qinLingensis, followed by membrane separation. Moreover, the mechanism for the hemicelluloses extraction will be revealed via using thermodynamic theory of vapor-liquid equilibria and reaction pathway of hemicelluloses dissociation as well as models of LCC and holocellulose. In addition, the structure of hemicelluloses from bamboo Fargesia qinLingensis will be characterized by monosaccharide composition, molecular weight, methylation analysis, SEM, AFM, FT-IR, and 2D HSQC NMR. Finally, the physicochemical properties of hemicelluloses such as rheology and thermal stability will be investigated. The objective of this project will provide the theoretical foundation for clean and efficient extraction of hemicelluloses from bamboo. Meanwhile, it will offer the scientific basis for high-value and efficient utilization of hemicelluloses from bamboo Fargesia qinLingensis and the bamboo resource in forestry.

竹材是我国林业重要的资源之一，半纤维素在竹材中的含量仅次于纤维素，且在竹产业化工领域具有广泛的应用前景。但目前由于缺乏对半纤维素清洁高效提取机理的研究，导致碱液和有机溶剂提取半纤维素存在分子降解和环境污染问题，严重制约了竹材半纤维素的高值化转化。本项目拟在研究秦岭箭竹半纤维素键合机制的基础上，采用γ-戊内酯/亚临界水清洁体系梯度提取秦岭箭竹半纤维素，利用膜分离得到结构较为均一的半纤维素组分。应用热力学气液平衡理论、半纤维素解离化学反应途径及LCC和综纤维素模型物揭示该技术提取半纤维素机理。此外，通过对半纤维素单糖组成、分子量和甲基化分析以及SEM、AFM扫描，结合FT-IR和2D HSQC NMR技术解译秦岭箭竹半纤维素分子结构，并对其流变性和热稳定性等理化性质进行研究。通过本项目的实施以期为竹材半纤维素的清洁高效提取奠定理论基础，同时为秦岭箭竹半纤维素及箭竹资源高值化利用提供科学依据。

竹材是我国林业重要的资源之一，半纤维素在竹材中的含量仅次于纤维素，且在竹产业化工领域具有广泛的应用前景。但目前由于缺乏对半纤维素清洁高效提取机理的研究，导致碱液和有机溶剂提取半纤维素存在分子降解和环境污染问题，严重制约了竹材半纤维素的高值化转化。本项目主要研究了γ-戊内酯/亚临界水梯度提取秦岭箭竹半纤维素机理以及秦岭箭竹半纤维素分子结构与理化性质。研究表明秦岭箭竹半纤维素γ-戊内酯/亚临界水梯度提取可选择性分级溶解不同分子量与结构的半纤维素，主要由木糖、阿拉伯糖和葡萄糖醛酸组成，随着γ-戊内酯浓度从80%逐渐降低至20%时，溶解的半纤维素分子尺寸由小变大，由支链型逐渐变为直链型，但同时也有一定的降解，分子量较大的半纤维素具有较好的热稳定性。结构研究表明，秦岭箭竹半纤维素为乙酰化L-阿拉伯糖-4-O-甲基葡萄糖醛酸木聚糖，其中阿拉伯糖和葡萄糖醛酸分别连接至木糖O-2和O-3位。本项目的实施能够为竹材半纤维素的清洁高效提取奠定理论基础，同时为秦岭箭竹半纤维素及箭竹资源高值化利用提供科学依据。